Electric regulation



2 Sheets-Sheet l Filed Jan. 2l, 1935 INVENTOR Hey/wr Mff/,fi

ATTORNEYS of the periods when the winding is :ie-energized, and otherfactors.

If therefore the winding is intended to control, through its inducedmagnetic flux, any related apparatus, mechanisms, circuits, or the like,the production of a critical value of flux must be dependent uponachievement of a fixed or critical value of current through the coil,but due to the variability of the resistance of the winding as abovepointed out, the voltage necessary to achieve this given value ofcurrent from the winding will necessarily vary with the variations inthe resistance.

Let it be assumed, for example, that the winding is to achieve, withrelated means, constancy of voltage in an electrical circuit; if thewinding and its related parts are so constructed as to regulate forconstancy of current (to produce the above mentioned flux), the voltageneces sary to maintain this constancy of current through the windingvaries with the change in resistance of the conductor of the winding,assuming that the winding ls bridged directly across the circuit thevoltage of which is to bei maintained constant. I'he result is that verysubstantial departures from the desired value! of voltage are caused bythe change in the resistance of the winding.

It has heretofore been proposed to counteract these effects by placingin series with the winding a relatively large external resistance ofzero temperature coeiiicient of resistance and such an arrangement hasbecome wide practice; the theory of such practice is that, by thusgreatly increasing the total resistance of the winding circuit, thechange in resistance that takes place within the winding itself becomesa small enough yfactor relative to the total circuit resistance totolerate the nevertheless inescapable fact of change in voltage ofregulation. However, such an arrangement does not remedy the difficultyand is moreover of limited scope of application, not to mention itswastefulness of material and electrical energy or low elllciency. Wherethe energy requirements of the winding or controlling coil arerelatively large, the applicability of this prior practice fails unlessmany disadvantages can still be tolerated.

For example, let it be assumed that the control winding has to beconstructed so large that its energy requirement is 100 watts; if thechange in resistance of such a winding causes a 15% voltage variationand if it is desired to reduce that variation to a maximum of 5%, it isnecessary to have connected in series with the winding an externalresistance which is twice that of the winding, the external resistancerequiring therefore that an additional200 watts must be dissipatedtherein. If the range of change of temperature of the control winding isstill greater, with corresponding change in' resistance. then everlarger values of external reistance must be used to reduce the ultimatevoltage variation. These instances illustrate some of the distinctdisadvantages of such prior practice which, in no case, it will be seen,achieve an entire absence of voltage variation. If the winding thereforeis employed for regulation of voltage, constancy of voltage cannot beand is not achieved.

One of the dominant aims of this invention is to do away with suchdisadvantages as have yjust been noted above and to provide a systemachieved, and maintained throughout the widely varying conditions ofpractical use.

Referring now to Fig. l of the drawings, I have there diagrammaticallyshown an electromagnetic Winding IU of the general character abovementioned; by way of illustration and to clarify a ready understandingof my invention, I have shown the winding I as the control or regulatingwinding in a system or apparatus for achieving constancy of voltageacross the circuit I|-I2, winding I0 being connected, as more clearlyhereinafter described, to be responsive to that function (voltage, inthis instance) of the electrical energy in the circuit I I-I2 which itis desired to maintain constant.

In so far as certain features of my invention are concerned, the windingID may control, affect, or actuate or coact with any desired or suitableparts or apparatus which are, by the Winding I0, made to effect acorrection of departures from the selected value of the function of theelectrical energy that it is desired to maintain constant. For example,the winding ID may be in the form of a relay for controlling aresistance which in turn is made to affect the voltage across thecircuit II--I2; thus, for example, a generator I3 (either alternatingcurrent or direct current) may be the source o! supply of electricalenergy to the circuit II--I2 and the resistance, illustratively in theform of a carbon pile I4, may, under the control oi.' the winding ID,affect the excitation of the ileld Winding l5 of the generator I3, thusto control the voltage of the output of the electrical source I3.

By Way of further illustration, the winding I0 may form part of asolenoid having a fixed core I 6 and a coacting movable core I'l, thesetwo parts being suitably shaped, as by tapering them as is indicated inFig. 1, so that, with respect' to thevmechanical resistance opposingmovement of the movable core Il, the winding I0, at a given or intendedenergization, will hold the core I1 in whatever position it is movedthroughout its range of movement. Movable core Il may be connected to abell crank lever I8 pivoted at I9, and having its one arm I8a operatingupon the free or unanchored end of the carbon pile I4. A spring 20opposes the pulling effort of the solenoid.

Disregarding resistance changes in the winding Ill, increase in voltageacross the circuit II--IZ increases the energization of the winding IDbeyond the value corresponding to the voltage desired to be maintainedconstant across the circuit II-I2, whereupon the pressure on the carbonpile I 4 is lessened, its resistance increased, and the resultantdecrease in the excitation of the generator I3 restores the voltage tonormal. Should the voltage decrease, a reverse action takes place inthat the corresponding decreased energization of the winding IU disturbsthe mechanical equilibrium theretofore existing and permits the spring2|) to swing the lever I8 in clockwise direction, thus increasing thepressure on the carbon pile I4 and correspondingly increasing theexcitation of the generator I3 to restore its voltage to normal.

As above pointed out, where the winding I0 is to respond to changes involtage, it is bridged across the circuit the voltage of which is to beaffected. Accordingly one terminal of winding I0 is connected byconductor 2| to one side, con ductor II, of the circuit II-I2; the otherterminal of winding ID is connected by conductors 22 and 23 to the otherside, conductor l2, of this circuit, but through a temperature-changecompensating device generally indicated at R.

The device R includes a member 24 having a negative temperaturecoeicient of resistance and has thermally related to it means giving thepart 24 a thermal capacity which is high compared to the thermalcapacity of the part 24 itself. 'Ihe winding I0 may be constructed inany suitable manner; whatever its physical construction, it embodiesnecessarily the mass of conductor (usually copper) of which it is woundtogether with such possible related parts as an iron core, parts eitherof solid dielectric material or of metal between which or upon which theconductor is wound, and like parts, giving the winding anultimatemasshaving a certain area of exposed surfaceor surfaces whichcan and do function as heat-radiating or heat-dissipating surfaces.Depending upon such factors as these, varying as they do with thedesign, purpose, power, or physical dimensions of the winding, thewinding is found to have a thermal capacity which is, relativelyspeaking, large, and it is found that the winding has a correspondingcharacteristic of rate of rise of temperature beginning with the flowtherethrough of its rated energizing current and hence also acorresponding characteristic of rate of decrease of temperature when theenergizing current is cut off. The relatively large ratio of thermalcapacity ofthe coil to cooling surface area ofthe coil makes this rateof change of temperature relatively low. The device R (Fig. 1) embodyinga relatively small part 24 (inherently of small thermal capacity) hasthermally related to it one or more members, illustratively two innumber as shown at 25 and 26 in Fig. 1, of a material like cast iron,steel, brass, or other suitable metal or material, in sufficient volumeor mass to give the device R, with respect to the latters heat-radiatingsurfaces, a high thermal capacity, and moreover a ratio of thermalcapacity to heat-radiating surface of device R that is equal to orcommensurate with the ratio of the thermal capacity of the winding Illto the heat-radiating surface of the winding l0. f

By way of illustration the part 24, having a negative temperaturecoefiicient of resistance and made of any suitable material having sucha coeicient, such as carbon', carbon compositions, psilomelane, galena,silicon, carbide, zincite, graphite, certain alloys (such as bronze madeup of 88% of copper and 12% of tin with a small quantity of phosphorus),may be in the form of a disk interposed between the ends of the parts 25and 26 which are made up in the form of preferably cylinders made, forexample, of cast iron.

The members 25-26 may or may not be included in the circuit of thewinding l though it is more convenient to include them in that they maythus also serve-as the contactors with the disk-like resistance element24; the crosssection of metal in the members 25-26 is suiilciently largevirtually in any case so as-notmaterially to aiect the resistance of thecircuit or to be materially affected by 13R losses therein. In any eventthe resistor 24, of negative temperature coeflicient and of small massand hence of small thermal capacity, is in the circuit of the Winding'i0 and has its thermal capacity greatly increased by being thermallyrelated to arelatively large mass such as the metal members 25-26. Asthe resistor 24 heats up, due to the ow of current therethrough, heatflows from the resistor 24 to the mass 25-26, the total mass of thedevice R being given such an external or other exposed heat-dissipatingsurface that the rate at which the temperature of the entire mass of thedevice R changes with flow of current through the resistor 24substantially matches1 or equals the rate of change of temperature ofthe winding l0. Depending upon the relative temperature coeiicients ofresistance and upon the relative ohmic resistances of the winding I0 andthe resistor 24, the mass of the part or parts 25--26 and theheat-dissipating surfaces thereof may be changed or determined tocontrol the. rise or fall of temperature of the resistor 24 withcontinued flow of current or cessation thereof respectively so thattheincrement of change of resistance in winding I0 in one direction isexactly counterbalanced by an equal increment of change in resistance inthe resistor 24 in the opposite direction.

With this arrangement exact or precise -regulation at the intendedvoltage may be accom# plished. The action achieved by the abovedescribed interrelation of the thermal capacities of the winding andresistor unit may be better understood if reference is now made to Fig.y'I of the drawings.

In Fig. '7 the curve A represents the voltage of the circuit beingregulated over a period of time beginning with the closure ofthe-regulating circuit (with the parts starting at room temperature)`and terminating at the end of three hours or so when, under the thereexisting conditions, steady conditions of ultimate temperature had beenachieved. CurveA is substantially a straight line with detectiblevariations therein of only a small .fraction of one per cent. departuresfrom the intended value of voltage to be kept constant. Curve Brepresents, for the saine period of time, the percentage variations ofvoltage across the coil I0 of Fig. 1, and shows a progressive increasein voltage from substantially zero to about 5%, representing the steadyincrease in voltage across the coil I0 necessary to maintain the currenttherein constant against the steadily increasing resistance accompanyingthe rise in temperature of the winding I0. Curve C represents thepercentage decrease in voltage across the resisor 24 of Fig. 1 and itwill be seen that curve C is geometrically similar to curve B, bothcurves clearly showing that for each increment of increase in resistancein the winding i0 there was a corresponding decrement in the resistanceof the resistor 24 and since the same current flows through both windingand resistor, the resultant voltage drops always tota-l the same,namely, the voltage of the circuit Il-l2. Where one voltage drop (thatacross the winding l0) increased, the other voltage drop (across theresistor 24) decreased in exactly the same extent.

Should the circuit of coil l0 be interrupted at rany time, the rates ofheat loss from the thermal masses represented by the winding l0 and bythe resistance device R will substantially follow the characteristics ofFig. 'i' so that, should the circuit of the Winding l0 be restoredbefore it is completely cooled olf, as might be the case where windingI0 operates intermittently, the temperatures of the winding l0 and theresistor 24 will have been maintained in their proper relations so thata subsequent closure of the` circuit finds the then existingtemperatureresistance condition of the winding I0 exactly compensatedfor by the then existing temperature-resistance condition of theresistor 24.

The regulation thus achieved will be seen to be virtually perfectinasmuch as curve A is virtually a straight line parallel to thehorizontal axis and is devoid of variations or tluctuations beyond avirtually imperceptible or immaterial small fraction of one per cent.,even though the temperature of operation varies throughout relativelywide limits. Fig. 8 shows by way of comparison the performance of mysystem and apparatus as compared with a regulating system and apparatusdevoid of the compensating features of construction and action abovedescribed; curve D is virtually a reproduction of curve A of Fig. 7 andagain shows the high precision at which constancy of voltage is achievedwhile curve E shows the rate of change and magnitude of change ofvoltage of regulation., during the period that the regulating coil warmsup to operating temperature, even though the control or regulatingwinding (of curve E) is in series with a resistance having a zerotemperature coeilicient of the type earlier above described; Withinpractical limits of energy consumption and of magnitude of externalresistance, curve E demonstrates how the best performance thusachievable is inherently characterized by a change in standard ofvoltage regulation that is great as contrasted with a small fraction ofone per cent. (curve D) achievable with my system and apparatus.

In Fig. 3 I have illustrated a possible modified form or physicalembodiment of the resistance device R, simply to illustrate that thedevice R may be given other forms than that shown in Fig. 1 and morespecifically described later herein in connection with Fig. 6. In Fig. 3the resistance element (corresponding to the resistor 24 of Fig. 1) maytake the form of a rod 21, made of any suitable material as abovementioned in connection with the resistor 24; the rod 21 has associatedwith it one or more masses of a material preferably metal in order toincrease its thermal capacity and by way of illustration I have shownthe rod 21 of Fig. 3 surrounded by three annular-like (see also Fig. 4)members 28, 29 and 30, preferably of metal, and strung on to the rod 21but in close thermal contact therewith. The members 28--29--30 areproportioned as to axial length and radial thickness to give the desiredheat-absorbing mass and the desired heat-radiating exposed surfaces, allof course appropriately proportioned with respect to the thermalcapacity and exposed heat-dissipating surfaces of`the winding |0, as wasdescribed in connection with the device R of Fig. 1.

Or, under certain circumstances, the resistor of the device R may takethe form of an electrolyte having a suitable temperature coefficient ofresistance, preferably negative. The electrolyte might comprise a 5%solution of nitric acid havlng'a temperature coetllcient of 0.015, or itmight be a 5% solution of copper sulphate whose temperature coeiliclentis -0.021; these electrolytes are mentioned purely by way of example. InFig. 5 the electrolyte 3| is contained in any suitable vessel orreceptacle 32 and immersed therein are suitable electrodes 33--34 towhich the conductors 22 and 23 (see Fig. 1) may be connected in order torelate the resistance device to the winding IIJ. The material of whichthe receptacle 32 is made is preferably a material of good heatconductivity and, With the body of the electrolyte itself and its ownthermal capacity, the receptacle is proportioned so that the resultantheat-radiating surface and thermal capacity are appropriate to cause itsrate of rise or fall in temperature to 5 match the rate of rise or fallin temperature 0i the winding I0. If desired or if necessary the thermalcapacity may be increased by increasing the mass or volume of thematerial of which the receptacle 32 is made or by relating to thereceptacle 32 one or more members or parts (broadly similar to the parts25-26 of Fig. l or to the parts 28--29-30 oi' Fig. 3) of metal or othersuitable material, such as the part 35 of Fig. 5. For example, if thereceptacle 32 is of a circular horizontal cross-section, the part 35 maybe in the form of a collar or ring extending about the receptacle 32 andbrought into intimate thermal contact with the latter and hence alsowith the electrolyte 3|.

I have above made brie! reference to Fig. 6 in which is shown invertical cross-section, on an enlarged scale, the resistance device R 0IFigs. 1 and 2, with its details. Turning, therefore, to Fig. 6, the diskor ring-shaped resistor 24 is shown interposed between the ends of themetal cylinders 25-26, while the parts 25 and 26 respectively aresuitably bored out (as is also the resistor 24, as at 24e) to permit thepassage through these three parts of a clamping bolt 36 to hold thethree parts 25-24--26 in secure assembled relation.

Preferably washers or gaskets 31.-36 of a suitable relatively softmetal, such as lead for example, are interposed between the contactingfaces of the three parts in order to insure uniform distribution of theclamping pressure throughout the affected portions of the resistor 24;this feature is of particular advantage where the resistor 24 is made upof a carbon or graphite composition or of a composition described indetail hereinafter. Also the lead washers 31-38 insure a good electricalsurface contact with the resistor 24 in that they yield and adjustthemselves to unintentional or unavoidable irregularities or variationsin the surface of the resistor 24 itself; and further, the washers31--38 provide good thermal contact between the resistor 24 and theparts 25--2S.

The clamping bolt 36 is threaded at one end or at its two ends toreceive the clamping heads or nuts 39--40 in order that the appropriateclamping pressure may be applied and maintained. But the clamping bolt36 also and conveniently serves to mechanically hold and thuselectrically connect to the device R two supporting brackets 4|42 ofmetal, being suitably apertured to let the clamping rod 36 passtherethrough. The parts are so related and shaped that the clamping rod36 is insulated from the metal parts 25--26 and also from the connectingand supporting brackets 4 I-42; for this purpose a tube-like insulatingbushing 44, provided with insulating washers or flanges 45--46, extendsabout the bolt 36 and through the apertures in the bracket 4| andcylinder 25 on the one hand and the apertures through the bracket 42 andthe cylinder 26 on the other hand. Metallic washers 41 and 48 restagainst the insulating parts 45-46 and underneath the nuts 39-40 andthus the parts 42, 26, 38, 24, 31, 25 and 4| are dependably heldtogether mechanically and reliably held in electrical interconnection toform a circuit therethrough which may be traced in the order in whichthese parts have 75 just been identified. Also a good thermal contact isassured between adjacent or engaging parts. By means of the brackets4I-42, the device R may be mounted on a suitable base 49 of insulatingmaterial (Fig. 6) as by screws or bolts 5|-52 which may be andconveniently are utilized also to bind or clamp the conductors 22 and 23(see Figs. 1 and 6) of the circuit in which the device R is to beincluded.

I have above mentioned, by way of illustration, certain specific'examples of materials which may be employed in my system and apparatusand which have a suitable negative temperature coelcient of resistance.Now in accordance with certain other features of my invention, I mayemploy for the material of the resistance ,medium, such as the resistor24 or 21 of Figs. 1 and 3 respectively,'material having thecharacteristic of changing its ohmic resistance with change in voltageapplied to the resistance material itself.

Such materials which substantially depart from Ohms law in that thecurrent flowing in the circuit is not necessarily proportional to thevoltage impressed are known as ynon-linear impedances, and may take theform of inductances with iron cores, thermionic vacuum tube conductors,gaseous discharge devices such as neon lamps or helium glow lamps,certain electrolytic conductors, and many other devices. Some devicesare' pure resistance devices and follow Uhm's law for direct current,such as an iron-1 cored inductance, while on alternating current, theimpedance of the device or its resistance to current flow, is dependentupon the impressed voltage and other factors, such as the frequency ofalternating voltage. Other materials have a practically instantaneousresponse to voltage variations, so that the characteristics do notdepend upon its immediately previous history, and therefore at any giveninstant the amount ci current flowing through the material de= pendeonly upon the voltage impressed at that instant and not upon the currentiiowing the previous instant.

.a material may he selected so that as the voltage impressed on thematerial increases, the current may increase at a greater Yrate thanwould 'he the case it current were always proportional to the voltageimpressed. lllhus, in a pure resistance with alinear impedancecharacteristic, the current will be proportional to the impressedvoltage as shown hy the lcurve F in Figure 9.

With a ncn-linear impedance material used lor the resistance unit, thecurrent may not he proportional to the voltage, as shown in curve G ciFigure 9. lin the latter, the current ci curve Gi increases much morerapidly with velt`= age than does the current oi curve F. Thus, ii in aregulating system a denite current change meist he made in the currentci energization of winding i@ (Figure l) in order to overcome achieve adesired change, the change involtage for a pure' linear impedance asexemplified iny curve F* will reduire the same percent variation inregulated voltage to achieve the required current change as is themagnitude oi the current change in percent of total current owing inwinding it.` However, if a nonlinear impedance material is used as theresistance element in the coil circuitni Winding lil, then it is readilyapparent that a small voltage variation will result in a relativelylarge change in current in winding in winding I0, the change inregulated voltage will be much less if a material of a non-linearimpedance characteristic such as shown in curve G is used rather than alinear impedance as in curve F.

In alternating current circuits, such an effect is obtainable veryreadily by placing an ironcored inductance in series with the windingi0, so proportioning the core in the inductance coils that the iron isnear or. beyond its saturation value at the voltage at which the systemis to regulate.

In both alternating and direct current circuits, materials which have apractically instantaneous response to voltage variations are ofadvantage due to their independence of the frequency of the systemvoltage, whether alternating or direct current.

One such material is commercially known as Thyrite, and is described inU. S, Patent No. 1,822,742 issued on September 8, 1931. This material,described in the General Electric Review of February, 1930, hasmechanical characteristics ysomewhat similar to those of dry-processporceoi -the current :flowing before the voltage was doubled. Thus, theresistor 24 of Figures l and 6, for example, may be in the form ci adisk or Thyrite, illustratively a disk or annulus oi about three inchesin diameter and about oneeighth of an inch in thickness. This material,moreover, also has a negative temperature coefcient or resistance inthat its resistance decreases with increase in temperature.

ln addition tcthe advantages resulting from the use of a resistor with anegative temperature cceiricient oi resistance, a resistor made up ofthis material such as Thyrite, achieves many marked advantages.Illustratively let it be assumed that the winding it) has the rollowingcharacteristics, namely, a resistance on the order or 100 ohms, anoperating voltage on the order ci 50 volts, and an operating current ora critical current or energization ci 0.5 ampere; iet it be assumed,also, that, in accordance with the past practice as hereinabove acrossthe resistance is 100 volts. i variation mechaineal friction andmagnetic hysteresis to l oi 3% in the current ci energization dueperhaps to any condition of electromechanical unbalance in a regulatingor relay system would result in a variation of 1.5 volts across thewinding and of 3.0 volts across the resistance making a total voltagevariation to which the system and apparatus is subjected of 4.5 volts.

lf, however, instead of using such a resistance in accordance with priorpractice, I use a resistor ci 'I'hyrite in" circuit with theabove-assumed winding such that the above-mentioned 3% voltage variation(increase in voltage drop across the winding il) due to the increase incurrent of energization) is effective, due to the alccvedescribedcharacteristic of the material, to produce a voltage drop across theresistance of only 0.25 volt, then the total voltage variation of thesystem, instead of being 4.5 volts, becomes the sum of 1.5 volts and0.25 volt and hence 1.75 volts, resulting in a total voltage variationof only about 1.2% of the total voltage of 150 volts of the circuits I|-|2. Thus the performance of the system and apparatus is vastlyimproved with respect to the voltage sensitivity of the system includingwinding I0 and resistor R, a relatively small voltage variationresulting in a large change in current of energization.

The resistance material, having the abovementioned novel characteristicsI may employ in various ways; for example, I may embody it in the forminwhich the resistors of Figs. 1, 3 and 6 are embodied, relating it toappropriate masses of appropriate thermal capacities and heat-radiatingsurfaces or I may let these resistances of Figs. 1, 3 and 6 take theform or forms above described, including the form in Fig. 5, relyingupon the negative resistance coeillcients of temperature and include inthe circuit of the corresponding resistor device R and winding I0 anadditional resistor made up of a nonlinear impedance characteristic; inFig. l I have diagrammatically indicated at 55 how the resistor of thismaterial may be thus included in the system and apparatus. In such caseI am enabled to reduce the size and thermal capacity of the resistor Rdue to the coacting eiect of the resistor 55. In such case also I maydispense in the resistor device R with a resistor having a negativetemperature coeilicient of resistance and use a resistance of zerotemperature coeflicient, retaining yonly the non-linear impedancecharacteristics of resistance, although commonly a resistance materialof non-linear impedance characteristic has also a negative temperaturecoemcient of resistance.

'I'he ratio of thermal capacity to heat-radiating surface of the deviceR, to meet any particular or desirable condition of operation, may,moreover, be achieved, or varied as may be desited, in any suitable ordesirable way; for example, and again considering illustratively theembodiment shown in Figure l and more in detail in Figure 6, if it isdesired to obtain a more rapid rise in temperature in the device R andto obtain a higher ultimate rise in temperature, the parts 25 and 26,illustratively cylindrical as above noted, may be given correspondinglysmaller dimensions, as by reducing the axial length, correspondingly toachieve a change in thermal capacity and in cooling surface. Forexample, and purely by way of illustration, let it be assumed, in Figure1 or 6, that the disklike resistance element 24 is made of theabovementioned Thyrite material and is approximately one-eighth of aninch thick and three inches in diameter; let it further be assumed thatthe characteristics of coil I0 are such that there is about a 40 C. risein temperature with an increase of about 15% in resistance of the coppercoil. By giving the solid cylindrical members 25 and 26, illustrativelymade of iron or steel, a diameter of 3" and an axial dimension of 3"each, the ratio ofthermal capacity of the device R to its heat-radiatingsurface becomes such that the resistance element 24 is subjected to a.rise in temperature of about C., just about appropriate to achieve theearlier abovedescribed compensation for the temperature rises or changesin the regulator coil 0 and its associated parts.

To illustrate further, let it be assumed, however, that the regulatorcoil I0 and its associatedl parts have such a ratio of thermal capacityto heat-radiating surface that the rise in temperature thereof is on theorder of 55 C. to 60 C. with a resultant increase in resistance, due tothis temperature rise, that may be 20% or more. To achieve the desiredcompensation in the device R, a greater rise in temperature therein isnow necessary and hence a different ratio of thermal capacity toheat-radiating surface. Appropriate compensation is achieved bydecreasing the axial length of the parts 25 and 26 and it so happensthat if they are now made about 2" in axial length instead of 3" asabove assumed, an appropriate ratio results to give exactly thecompensation fdesired, as earlier above described in detail; inl suchcase, the rise in temperature of the disk-like resistance element 24 isapproximately C. to 120 C.

These two illustrations will suffice to illustrate in detail suchchanges, based upon two illustrative but diiferent practicalrequirements, that may be made to obtain a ratio of thermal capacity toheat-radiating surface of the device R that substantially matches theratio of thermal capacity to heat-radiating surface of the coil and itsassociated parts.

However, other means may be employed to obtain the desired ratio. Forexample, and referring now to Figure l0, and'assurning that the coil I0and its related parts require, in the device R, a lower ratio of thermalcapacity to heatradiating surface, I may provide the parts 25 and 26, oreither of them, with, for example, heat-radiating fins 60. Or the parts25 and 26 may be hollowed out or counterbored, as at 25* and 26X. Or, aswill now be clear, I may select any appropriate material of which tomake the parts 25 and 26, selecting the material in accordance withitself, and appropriately dimensioning the part or parts of suchmaterial; for example, iron has a specific heat of 0.1138, aluminum0.2143, lead 0.0314, and so on.

I may achieve the desired ratio of thermal capacity to heat-radiatingsurface of the illustrative parts 25 and 26, or either of them, bydimensioning the parts to have the desired thermal capacity and thendiminish the existingheat-radiating surface thereof as by covering anappropriate portion of the otherwise available heat-radiating surfacewith a good non-conductor of heat, such as asbestos in appropriatethickness. In Figure 11 I have shown the parts 25 and 26 provided with awrapping, of appropriate axial extent, made of such heat-resisting orinsulating material, as is indicated at 6i.

And, as will now be clear, the desired ratio may be achieved, changed,or altered, with respect to the device R of Figures 3 and 5, in mannersand by means such as those illustratively just described.

Thus, it will be seen that there has been provided in this invention anapparatus in which the objects above-mentioned, together with manythoroughly practical advantages, are successfully achieved. It will beseen that the nvention is of a thoroughly practical character, and is inaction dependably precise, and is, moreover, well adapted to meet thevarying conditions met with in practice.

as many possible embodiments may be made o1' the above invention and asmany changes might be made in the embodiment above set forth, it is tobe understood that all matter hereinbefore set forth, or shown in theaccompanying drawings, is to be interpreted as illustrative and not in alimiting sense.

I claim:

1. In a system of electric regulation, in combination, a circuit havingtherein electromagnetic means for controlling a regulating means, y,saidelectromagnetic means having a certain ratio of thermal capacity toheat-radiating surface thereof and having a positive temperaturecoefficient of resistance, and means in circuit with saidelectromagnetic means and having a negative temperature coeiiicient ofresistance and substantially the same ratio of thermal capacity toheat-radiating surface as said electromagnetic means.

2. In a system of electric regulation, in combination, a circuit havingtherein a regulating coil of given ratio of thermal capacity toheatradiating surface and having the characteristic of change inresistance with change in temperature thereof due to 12R loss therein,and means for maintaining the current through said coil substantiallyconstant in spite of change in resistance thereof comprising aresistance element having the characteristic of .changing its resistanceas its temperature increases due to 12R loss therein in a directionopposite to the direction in which the resistance of said coil changes,and means thermally related to said resistance element to give it athermal capacity and heatradiating surface such that the ratiotherebetween is'substantially the same as said firstmentioned ratio.

3. In a system of electric regulation, in combination, a circuit havingtherein a regulating coil Whose impedance changes with change inoperating temperature and having serially related thereto a.compensating impedance means, the ratio of thermal capacity toheat-radiating surface of said coil and of said impedance means beingsubstantially the same.

4. In a system of electric regulation, in combination, a circuit havingtherein a translating device in which is included conductive means whoseimpedance' changes with change in operating temperature, and means formaintaining the current in said circuit substantially constant asagainst the change in impedance of said conductive means comprisingconductive means connected serially with said rst-mentioned conductivemeans and having the characteristic of changing its impedance wi@ changein operating temperature but in a direction opposite to the direction inwhich the impedance of said first-mentioned conductive means changes,and means thermally related to said second-mentioned conductive means togive it a thermal capacity and heat-radiating surface such that theratio therebetween is substantially the same as the ratio being thethermal capacity and heat-radiating surface of said translating device.

5. In a system of electric regulation, in combination, a circuit havingtherein a translating device in which is included conductive means whoseimpedance changes with change in operating temperature, and means formaintaining the current in said circuit substantially constant asagainst the changelin impedance of said conductive means comprisingconductive means cong nected serially with said iirst-mentionedconductive means and having the characteristic of changing its impedancewith change in operating in impedance from materially affectingthestandard of voltage regulated by said regulating means comprisingcompensating impedance means electrically related to said regulatingmeans, the ratio of thermal capacity to heatradiating surface of saidregulating means and of said compensating impedance means beingsubstantially the same.

7. In a system of electrical regulation, in combination, a circuithaving therein a translating device which has a certain thermal capacityand a certain heat-radiating surface and having the characteristic ofchanging its impedance with changes in operating temperature, andcompensating impedance means electrically related thereto and comprisingan impedancev device having the characteristic of changing its impedancein the opposite direction with change in operating temperature butphysically having a ratio of thermal capacity to heat-radiating surfacedifferent from the ratio of the thermal capacity to heat-radiatingsurface of said translating device and means physically related to saidimpedance device to give it an effective ratio of thermal capacity toheat-radiating surface substantially equal tothe ratio of thermalcapacity to heat-radiating surface of said translating device.

8. A system as claimed in claim 7 in which the impedance device is inthe form of a disklike member and in which the means physically relatedto the impedance device comprises a metallic means of appropriate massand heatradiating surface.

9. A system as claimed in claim 7 in which the impedance device is inthe form of a disk-like member and in which the means physically relatedto the impedance device comprises two metallic means, each adjacent to aface of said disk-like member and being together of the desired mass andheat-radiating surface.

10. A system as claimed in claim 7 in which the impedance device is inthe form of a disklike member and vin which the means physically.related to the impedance device comprises two metallic means and meansfor holding them and said disk-like member together with the latterbetween them.

11. A system as claimed in claim 7 in which the impedance device is inthe form of a disklike member and ln which the means physically relatedto the impedance device comprises two metallic members between whichsaid disk-like member is positioned, and means extending through allthree and insulated therefrom for holding them in cooperative physicaland thermal relation.

l2. A system as claimed in claim 7 in which the means thermally relatedto the impedance device comprises a hollow member.

13. A system as claimed in claim 7 in which the means thermally relatedto the impedance thermal capacity and having means for reducing itsheat-radiating surface to the desired eX- tent comprising means ofsuitable resistance to conducting heat covering a desired portion of theheat-radiating surface.

14. A system as claimed in claim 'l in which the impedance devicecomprises a material having also the characteristic of changing itsresistance at a greater rate than but inversely to the rate of change ofvoltage impressed thereacross.

15. A system as claimed in claim 7 in which the impedance device is inthe form of a disklike member and in which the means physically relatedto the impedance device comprises two metallic means, each adjacent to aface of said disk-like member and being together of the de-` sired massand heat-radiating surface, and in which there is interposed betweeneach of the two metallic means and the disk-like member means of goodthermal conductivity for insuring good thermal interrelation between themember and said two metallic means.

16. In a system of electric regulation having a work circuit that has anauxiliary regulating circuit connected thereto with electro-responsiveVregulating means in said regulating circuit, the latter having thecharacteristic of changing its impedance with changes in operatingtemperature, the combination therewith of an impedance device in serieswith said electro-responsive means and having the characteristic ofchanging its impedance so that the current iiow therethrough issubstantially a logarithmic function of the voltage, the ratio ofthermal capacity to heat-radiating surface of said regulating means andof said impedance device being substantially the same.

1'7. In a system of electric regulation, in combination, a circuithaving therein an electrical unit whose impedance changes with change inoperating. temperature and having serially related thereto compensatingimpedance means, the ratio of thermal capacity to heat-radiating surfaceof said unit and of said impedance means being substantially the same.

18. In an electric circuit, in combination, an electrical unit whoseimpedance changes with changes in operating temperature, and acompensating impedance means, the ratio of the thermal capacity to theability to dissipate heat to the surrounding medium of said unit and ofsaid impedance means being substantially the same.

19. An electrical circuit which includes a plurality oi electrical unitsone of which is a compensating impedance means whose impedance changeswith a change in operating temperature and Whose heat-retaining,heat-absorbing and heat-dissipating characteristics are such that with agiven variable voltage impressed upon the circuit the temperature ofsaid impedance means will at all times be the same as the temperature ofanother unit in the circuit.

20. In an electric circuit, an electrical unit having impedance whichchanges as the operating temperature changes and including portionshaving heat-generating, heat-accumulating and heat-dissipatingcharacteristics, and a compensating impedance unit having impedancewhich changes as the operating temperature changes including portionshaving heat-generating, heataccumulating and heat-dissipatingcharacteristics, said characteristics of said units being substantiallysimilar.

2l. A circuit as claimed in claim 20 in which the compensating impedanceunit has -two substantially cylindrical metallic blocks in spacedalignment and a substantially disc-shaped resistance element between theadjacent ends of said blocks.

22. A circuit as claimed in claim 20 in which the compensating impedanceunit includes a rodlike resistance element and Washer-like metallicmembers fitted upon said rod.

23. A circuit as claimed in claim 20 wherein the compensating impedanceunit includes a substantially cylindrical portion and washer-likemetallic elements mounted upon said substantially cylindrical portion.

24. A circuit as claimed in claim 20 wherein the compensating impedanceunit includes a heat-insulating covering which may be adjusted so as tocontrol the heat-dissipating characteristics of the unit.

25. A circuit as claimed in claim 20 in which the compensating impedanceunit includes two bracket members adapted to act as mountings for theunits and for Wire terminals, two substantially cylindrical metallicelements mounted between said brackets in substantial alignment, asubstantially cylindrical resistance element mounted between theadjacent ends of said substantially cylindrical metallic elements, boltand nut structure holding said elements and said rod elements in place.

FRANK W. GODSEY, JR.

